Parallel import is based on the principle of consumption. Original goods, which have been brought on the market legally, may normally be resold without the permission of the rights owner. In other words, the rights of the rights holder are exhausted (consumed) through the original sale.
When a product is sold in a country within the EU/EEA, it may be freely sold in the entire EEA, which consists of the countries in the European Union together with Iceland, Norway and Lichtenstein. If the product has not been sold in the EEA, it may not be sold in the EU without permission from the rights holder. If so, it is a case of illegal parallel import.